Ethernet VPN (EVPN) uses the Border Gateway Protocol (BGP) as control-plane for MAC address signaling and learning in data center fabric networks, as well as for access topology and VPN (virtual private network) endpoint discovery. Such networks typically comprise core switches that connect interconnect servers, and edge switches that connect client devices to the network. For network access using native Ethernet frames, the core would have the frames encapsulated with a VXLAN header, with a control plane running between devices interconnected by the core. EVPN expands current existing Virtual Private LAN Services offerings by using control-plane based MAC learning over the core. In EVPN networks, a software MAC address table is maintained in the firmware of network switches and/or other router devices. This MAC address table contains the MAC addresses learned on all the interfaces of routers and Ethernet access switches. Dynamic MAC address learning occurs when the bridging data path encounters an ingress frame whose source address is not present in the MAC address table for the ingress service instance. In EVPN, the system learns addresses on access interfaces, and uses a protocol, such as BGP, to learn addresses of the access interfaces on other switches in the network.
The Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems on the Internet. BGP makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator. Internet Service Providers (ISP) use BGP to establish routing between one another and very large private IP (Internet Protocol) networks may use BGP internally. BGP neighbors are called peers, and are established by manual configuration between routers using TCP as the transport protocol.
EVPN enables users to connect different customer sites at layer 2; in other words, frames are forwarded between customer sites based on the contents of the layer 2 header. The VXLAN (virtual extensible LAN) overlay allows the network to stretch layer 2 connections over intervening layer 3 networks, thus providing for network segmentation without VLAN scaling limitations. VXLAN is virtualization technology that was developed to address the scalability problems associated with large cloud computing systems, thus EVPN with VXLAN encapsulation handles layer 2 connectivity at the scale required by cloud service providers. Virtual link trunking (VLT) was developed by Dell Networking to allow users to set up an aggregated link towards two different switches by making them appear logically as a single switch to the peer, where a standard aggregated link can only terminate on a single switch. It is a layer-2 link aggregation protocol between end-devices (servers) connected to different access-switches, offering these servers a redundant, load-balancing connection to the core-network in a loop-free environment. VLT can also be run between switches, such as between an access switch and multiple core switches.
In BGP-EVPN, when VLT is used to provide multi-homing for customer hosts, it is possible that traffic destined to the orphaned (single-homed) hosts which are connected to VLT peers might take a sub-optimal path. It would be advantageous to avoid these sub-optimal paths to the orphaned hosts. It would also be advantageous to provide a method that determines how the unicast and multicast traffic is delivered to multi-homed and orphaned hosts in a VLT domain.
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.